Liquid fuel supply systems for gas turbine engines



s. R. TYLER Feb. 24, 1959 LIQUID FUEL SUPPLY SYSTEMS FOR GAS. TURBINE ENGINES Filed April 5, 1957 SP/LL BURNER (5) WITH SW/PL C/RCULA TING F j CH/I MB ER TURBINE DRIVEN 5v PUMP /2 mi ERR NM R U58 5 M A P W NVENTOR STANLEY A? TYLER BY ,6, ,Z; W

ATTORNEYS n td5ta at o TttisHnventibm relates to; apparatit'sli' ,whieli liquid fuel is fed- 'to liurnet'sor equivalent'df the spill type of a gas turbine eng in inafter. simply referred to as burners, wlffibi W edito'itifc'liide'alTsuch equivalents) by means pos e displ cement pump, and the: object of the invention is to? provide? improved: vmeans fv z s st w nflthe omiza ion o thel'fuel Part ul y when BJI'BIIRPIZYCIXSEQQH quantity of fuel-r-is being discharged hr u hammal t t. M

A iqu da us su pl y temfor 1838- turbine en av tb mcrsgfjh sp ll ypesuppli m th fu l-u de 1d splacem tn mp qludesi 1 p re y a p.0 accordance with the invention a circulating pump provided in a closed circuit including the swirl chambers of the burners, and a motor in driving connection with the circulating pump arranged to be driven by surplus fuel which is by-passed from the output of the positive displacement pump. As less fuel is delivered to the burners, more enters the turbine motor in the by-pass passage, that drives the circulating pump, augmenting the circulation of fuel through the burner, and so improving atomization of the fuel.

Two embodiments of the invention will now be described with reference to the accompanying diagrammatic drawings of which Figure 1 shows one embodiment and Figure 2 the other.

As shown in Figure 1, liquid fuel from a tank 11 is fed by an engine-driven pump 12 of fixed volumetric displacement to the burners of the engine one of which is indicated at 13. The rate of supply of fuel to the burners 13 is regulated by a servo-operated by-pass valve 14 of the pressure-balanced type situated in a by-pass passageway 15 extending between the delivery and inlet sides 16 and 17 respectively of the pump 12, the by-pass valve servo mechanism forming part of a flow control device 18 having a manual control lever 19 and situated in the delivery line 20 from the pump 12 downstream of the by-pass passageway 15. The burners 13, of which there would normally be several, are of the known spill type, having each a swirl chamber whence a fuel spray is delivered to the engine and the surplus is returned to the inlet side of a circulating pump, the common spill line 21 of all the burners being connected to the eye or inlet of a centrifugal pump 22. The outlet side of the pump 22 is connected with the delivery line 20 at a point therein which is downstream of the flow control mechanism 18. A non-return valve 23 is situated adjacent the outlet of the circulating pump 22 and serves to prevent return flow from the delivery line 20 to said pump 22. The centrifugal pump 22 is adapted to be driven through a shaft 24 of a turbine 25 situated in the by-pass passageway 15, the inlet of the turbine 25 being connected to the delivery side of the pump 12 whilst its eye or outlet is connected with the by-pass valve 14 at the inlet side of the latter.

The speed of operation of the centrifugal pump 22 will depend upon the conditions prevailing in the normal fuel supply system; Assuming 'arffe irtrme base in the fuel delivered by the enginedriverfpuirrpil chargedthrkiuigli the burners l3i'thefe w ill' lie" 11 rue: flpwi'n along the bypass-passageway so-{tli the: turbine 25*will-l riot receive any d ce'n irugaipum 2f2 wi1r15e tanomry;' regress dischar ed tlirbu'gh' the burners 13' with? increased it along the by-pass passageway 1 5 ;v the" tix'rbiifjfi di i ve n at a corresponding rat and the 22 will now rintlthusimproving ltlie'atbtiuza q Referring now to tlie' mndifiedflenip mi: of? invention illustrated by- Ei ie 25in wt: Iilt T Figure: 1 are given" like? refererice'nuinera s 'the servo; operatea by ass va ue; 1 4 and the Hy-passp ssggeway" 15% across the engine drigen pump 12 areinaependenror fie supply] of fuelthrong ttie'tnfliiiiecs ranslator-sna ply' 'is adapted to tat laceaioiig a furttier uy pass p as; sageway 2fi e'xtending across the?en'girie lir'ive'nr puifip The supply: of fuel to theturbine=25 is regu ate by' a' throttlevalve-'27" situat'ed iti SaiCl t-urthofi wpa'sspassage way 26: preferably; as shoWri=-, at the outlet side ofi'tlie turbine 25. The throttle valve 27 is:serlvo opezatdluhdeh the. controlofa known; form: ofsadiaphragnwient control devieeg28ywhichisresponsivegto thelpressumtdiflerencc existing across the burners 13, one side of said diaphragm device 28 being connected by a pipe line 29 with the inlet sides of the burners 13 whilst the other side of said device 28 is connected by a pipe line 30 with the common spill line of the burners. When there is a large pressure difference across the burners, the servo vent 31 associated with the throttle valve 27 will tend to close which tends to cause the throttle valve 27 to restrict the passage leading from the outlet of the turbine. As the pressure difference across the burners 13 reduces, so the vent of the throttle valve 27 tends to open to permit said throttle valve to move to enlarge the passage from the turbine 25.

If the fuel is being supplied to the engine burners through two or more engine-driven pumps operating in parallel and constituting in effect a multi-stage pump, the system may include valve mechanism whereby when a pump is not required to deliver fuel to the burners its output may be diverted to the inlet of the turbine for driving the centrifugal circulating pump instead of, as is usual, diverting its delivery back through a by-pass valve to tank.

In all cases, fuel displaced by the engine-driven pump means and not required for supplying the engine burners is Wholly or partly utilised for driving the turbine and thus increasing the circulation of fuel passing through the swirl chambers of the burners or equivalent.

I claim as my invention:

1. A fuel supply system for a gas turbine engine, said system comprising at least one spill spray nozzle, a circulating pump, a closed circuit for delivering fuel from the circulating pump to the nozzle and for return of unused fuel to the circulating pump, a positive displacement supply pump to supply fuel under pressure into the closed circuit, a by-pass passage means connecting the inlet and the outlet of the supply pump, and a valve therein arranged to withdraw fuel from the output of the supply pump, fuel flow control means acting on the bypass valve to control fuel flow from the output of the supply pump to the closed circuit, and a liquid-operated motor in driving connection with the circulating pump and driven by fuel withdrawn into the by-pass passage from the output of the supply pump. w

2. A fuel supply system fora gas turbine engine employing at least one spill burner having a swirl chamber, said fuel supply system including a positive displacement supply pump, a circulating pump, a fuel conduit including a delivery line leading from the circulating pump and adapted for connection to the swirl chamber and a return line adapted for connection to the swirl chamber and leading to the circulating pump, a liquid-operated motor outside said fuel conduit operatively connected to drive the circulatingpump, and a branched conduit leading from the outlet: of the supply pump, one branch leading to the fuel conduit to make up fuel discharged at theburners, the second branch leading to and driving the liquidvoperated motor.

, 3.'A fuel-supply system as in claim 2, including a return connection from the liquid-operated motor to the low pressure side of the supply pump, constituting, with the second branch leading to the supply pump, a by-pass passage, and fuel flow control means in said by-pass passage regulating flow therethrough.

4. A fuel supply system as in claim 3, wherein the fuel flow control means includes a by-pass valve located in the return connection, intermediate the liquid-operated motor and the low pressure side of the supply pump.

5, A fuel supply system as claimed in claim 4, wherein the fuel flow control means is controlled by the pressure dilference existing between inlet and outlet of the spill nozzle such that reduction'of this pressure difference will increase the fuel flow controlled by the by-pass valve to the liquid-operated motor.

6. A fuel supply system as claimed in claim 5, including'a further fuel flow control means and a further bypass valve controlled by the further flow control means to withdraw fuel from the output of the positive displacement pump.

7. A fuel supply system for a gas turbine engine, said system comprising at least one spill spray nozzle, a centrifugal circulating pump, a closed circuit including the circulating pump for delivering fuel from the circulating pump to the nozzle and for return of unused fuel, a positive displacement supply pump to supply fuel under pressure of a capacity exceeding the nozzles maximum requirements, a by-pass passage means for withdrawing fuel from the output of the positive displacement pump, a by-pass valve in the by-pass passage for controlling such withdrawal, fuel flow control means acting on the by-pass valve to control fuel flow from the output of the positivedisplacement pump to the closed circuit, and a turbine in driving connection with the circulating pump and driven by fuel withdrawn by the by-pass passage and valve from the output of the positive displacement pump.

References Cited in the file of this patent UNITED STATES PATENTS 2,23 8,502

Angell Feb. 19, 1957 

